Process of treating smokeless powder



Patented July 12, 1938 UNITED STATES PATENT OFFlCE I Richard G. Woodbridge, Wilmington, Del., as-

signor to E. I. du Pont de Nemours & Company, Wilmington, DeL, a corporation of Delaware I No Drawing. Application December 2'7, 1935,

Serial No. 56,343

20laims.

The object of my invention is to restore the chemical stability of nitrocellulose smokeless powders which have undergone deterioration during storage and at the same time to conserve 5 the ballistic qualities of the powder. My invention, while not limited to such, is particularly applicable to smokeless powder of the so-called Pyro type, that is, powder made from nitrocellulose with a nitrogen content of 12.50 to 12.70%

having a solubility in ether-alcohol mixture in excess of 95% of which more than one billion pounds were made during the World War in the United States for the use of the Allied Governments.

my application, Serial No. 678,731, filed July 1, 1933, which resulted in U. S. Patent 2,033,217, on March 10, 1936.

It is well known that smokeless powder deteriorates during storage. As more than 16 years have elapsed since the end of the World War the Pyro cannon powder made during the stress of war time conditions is approaching the end of its useful life. This is particularly true since Pyro cannon powder of war time manufacture was for the greater part water-dried, that is, steeped in hot water in order to remove to the desired degree the volatile solvents, ether and alcohol, used in its manufacture.

Up to the present time deteriorated nitrocellulose smokeless powders of the y o type have been reworked by a process involving pulverizing the powder grains under water bymeans of a heavy wheel mill and subjecting the finely divided material a; a repurification treatment similar to that e loyed in the regular poaching treatment of the original nitrocellulose. Smokeless powder reworked in this manner has a relatively limited storage life because the process does not \completely remove the deteriorated products. For that reason the reworked powder is usually assigned for practice use.

A principal object of my invention is to restore the chemical stability of the deteriorated powder while still retaining the powder grains in their original form, thus avoiding the expense of grinding and reworking deteriorated nitrocellulose smokeless powder, besides the accompanying hazards of manufacture.

In my co-pending application, Serial No. 678,731, aforesaid, I have described one embodl-' ment of my invention in which distortion and cracking of the powder grains are minimized by subjecting them to a soaking treatment at room itcmperaturainordertopermitthearainsto This application is a continuation-in-part of swell slowly, before subjecting them to extraction in boiling alcohol. However. this treatment tends to increase the brittleness of the powder grains, particularly the larger grains, since the viscosity of the nitrocellulose is reduced in pro-'- 5 portion to the temperature and the time of extraction by means of the boiling alcohol.

I have now found that increased brittleness of the treated powder grains can be minimized and a still further decrease in the distorted and cracked grains can be obtained by carrying out the entire rejuvenation treatment at a temperature considerably below the boiling point of the ethyl alcohol, as, for example, at a temperature of 30 C. to 40 C. 15

One embodiment of my invention, as applied, to deteriorated Pyro cannon powder of the 155 m/m granulation, is more fully described as follows:

The nitrocellulose powder grains are covered with ethyl alcohol by volume) and subjected to a soaking treatment of five days at a temperature of about 30 C. The temperature of the alcohol is then gradually raised to 40 C. and the treatment continued at this temperature for about 25 nine days with several changes of alcohol until the dlphenylamine content of the powder grains has been reduced to about 0.02%. The extracted powder grains are then subjected to treatment in an alcoholic solution of new diphenylamine, containing about 1.25% of diphenylamine based on the weight of the powder. This treatment is carried on for two to three days at 40 0.. preferably with circulation of the solution, until thepowder grains have taken up the desired amount of diphenylamine, in this case about 0.50%. The amount of diphenylamine put back into the powder grains can be varied according tothe amount of diphenylamine present in the dipping or rejuvenating solution. The excess alcohol is removed from the powder by draining or by wringing in a centrifugal wringer after which the powder is steeped in hot water at a temperature of 40 to 55 C. until the residual solvent or alco- 45 hol content of the powder grains is reduced to the desired figure. The powder grains are than air dried at about 55 C. for one or more days and finally conditioned to the desired moisture content.

The alcohol used may, of course, be denatured alcohol, such as formerly known as 23 containing 0.5 gallon benzol per gallons ethyl alcohol, or other suitable grades of denatured alcohol.

The time of treatment can of course be varied so long as it is maintained until the powder is freed from objectionable products of decomposition.

As many apparently widely difierent embodiments of this invention may be made without departing from the spirit thereof, it is understood that I do not limit myself to the foregoing examples or descriptions except as indicated in the following patent claims.

I claim:

1. The process of restoring the chemical stability of oliphenylamine-stabilized nitrocellulose powder grains while retaining the grains in substantially their orignal form, whch comprises treating the grains with ethyl alcohol at a temareas 17 perature of approximately 30 8., gradually raising the temperature to about 40 (3., maintaining such temperature until the powder is freed from objectionable products of decomposition, and impregnating the powder grains with fresh diphenylamine in alcoholic solution.

2. The process of restoring the chemical sta- Yoility of diphenylamine-stabilized nitrocellulose powder grains while retaining the grains in substantially their original form, which comprises 10 RICHARD G. WOODBRIDGE. 

